--- name: ? status: compiling version: 0.0.0 maintainer: Neo dependencies: [patience] ---
drafting spec…
the universe did not have a file for this yet. writing one now. (first visit only: future readers will see this page instantly.)
--- name: ? status: compiling version: 0.0.0 maintainer: Neo dependencies: [patience] ---
the universe did not have a file for this yet. writing one now. (first visit only: future readers will see this page instantly.)
--- name: Leap Seconds slug: leap-seconds type: temporal patch status: deprecated version: 0.1972.0 released: 1972-06-30T23:59:60Z maintainer: International Earth Rotation and Reference Systems Service (IERS) dependencies: - UTC - atomic-clocks - earth-rotation - human-stubbornness license: Public Domain (you did not consent to this) tags: - time - infrastructure - chaos - astronomy - deeply-annoying ---
A one-second adjustment inserted into Coordinated Universal Time because the Earth refuses to rotate at a consistent pace and we decided that was our problem to fix.
Atomic clocks are extremely good at time. The Earth is not. Every so often, the planet's rotation drifts enough that civil time diverges from astronomical time by almost a full second. The IERS, a small group of people with enormous responsibility and very little media coverage, then announces that 23:59:59 will be followed by 23:59:60 before midnight arrives.
This is not a joke. That timestamp exists. Schedulers, databases, and junior engineers have all encountered it unprepared.
The correction is applied at the end of June 30 or December 31. No fixed schedule. Just a letter from the IERS. Surprise.
| Bug ID | Description | Status |
|---|---|---|
| LSB-001 | time() + 1 does not always equal one second later | Won't fix |
| LSB-002 | Distributed systems briefly disagree on what time it is | By design, apparently |
| LSB-003 | Some NTP implementations handle the extra second by lying about it | Workaround accepted |
| LSB-004 | GPS time does not include leap seconds, creating silent divergence | Open since 1980 |
"We just smeared the second across the whole day. Nobody noticed. We're fine." — Google, describing "leap smear," which is a real thing they do
leap_second:
enabled: true # you don't get to set this
notification_period: ~6_months
insertion_points:
- 1972-06-30T23:59:60Z
- 1972-12-31T23:59:60Z
# ... 25 more through 2016
next_scheduled: unknown
abolition_vote: passed # see Deprecation Notice
In November 2022, the General Conference on Weights and Measures voted to abolish leap seconds by 2035. The exact mechanism for handling accumulated drift after that point is, at time of writing, "to be determined." The can has been kicked into the 2130s, when the problem will be revisited by people who are not yet born.
This module will be sunset. The Earth's rotation will not be.
Why don't we just update the definition of a second? Because atomic time is more useful than your intuition about what noon should feel like.
Has a leap second ever caused a real outage? Reddit, LinkedIn, Cloudflare, and others have all filed incident reports. The leap second has a better track record of causing chaos than most intentional load tests.
Can I opt out? You are already in. You have always been in.